Automate tagging of monthly release

What does this MR do and why?

Describe in detail what your merge request does and why.

Content

• Automate tagging of monthly release

Instead using ChatOps command, tag the monthly release using a release pipeline job, to improve visibility and automaticity.

• Add rake tasks to notify and perform tagging of monthly release.
• Add CI jobs to notify and perform monthly tagging:
  • After the monthly_release_tag_day:ensure_stable_branches_green and monthly_release_tag_day:mirror_status jobs completed successfully, notify about the start of tagging
  • Automatically start the tagging step after the notification
• Update the monthly issue template for this change.

Testing

❗ This is to test the tagging of monthly releases. I used the same test branch that I used in this testing (with the addition of the changes here). !3491 (merged)

Pipeline creation

With MONTHLY_RELEASE_PIPELINE=true	With MONTHLY_RELEASE_PIPELINE='tag_day'
Pipeline	Pipeline

Configuration testing

This was to test the pipeline configuration (the job order). I updated the jobs monthly_release_tag_day:start , monthly_release_tag_day:ensure_stable_branches_green and monthly_release_tag_day:mirror_status to echo the bundle rake tasks and disable the monthly_release_tag_day:check_omnibus_packages_tagging to just focus on the tagging step.

Step	Screenshot
Initialized as a manual pipeline	Pipeline link
After monthly_release_tag_day:start is manually triggered
The job monthly_release_tag_day:start_tag will automatically start after the jobs monthly_release_tag_day:ensure_stable_branches_green and monthly_release_tag_day:mirror_status completed successfully
Slack notification
The job monthly_release_tag_day:tag will automatically start after the monthly_release_tag_day:start_tag
Slack notification after tagging of monthly release	Test output message

Pipeline, Testing commit

Related Issue: gitlab-com/gl-infra/delivery#20472 (closed)

Author Check-list

• Has documentation been updated?